1. Field of the Invention
This invention relates to a composition and process for controlling the gelation time of alkali metal silicate-containing compositions. More particularly, it relates to a composition and process for controlling the gelation time of an alkali metal silicate-containing composition useful for stabilizing soil by incorporating therein certain compounds which modify the gel time of the silicate composition, the resulting gelled composition being characterized by enhanced load-bearing capacity.
2. Description of the Prior Art
It has long been known to produce gelled, cement-like masses from aqueous solutions of alkali metal silicates by the addition of salts of metals other than alkali metals, for example, aluminum, zinc, cadmium or iron. As described in U.S. Pat. No. 2,968,572 (Peeler), issued Jan. 17, 1961, it is further known to render soil impermeable to fluid and/or to strengthen it by injecting into said soil a composition comprising an aqueous alkali metal, e.g., sodium silcate, and a soluble amide such as formamide, acetamide, propionamide, butyramide and the like, said composition likewise containing, if desired, a reactive salt such as calcium chloride or sodium chloride to further customize the gelation time of the silicate. During gelation of the composition and thereafter, however, gaseous ammonia is liberated from the silicate-amide reaction, constituting a hazard to those working nearby, particularly in confined areas.
In U.S. Pat. No. 3,306,758 (Miller), issued Feb. 28, 1967, there is described an alkali metal silicate-containing soil stabilizing composition improved over that set forth in the aforesaid U.S. Pat. No. 2,968,572, in that no significant quantities of ammonia vapors are released upon applying and reacting the silicate and amide components. This improvement is effected by incorporating a lower alkyl aldehyde, e.g., formaldehyde, acetaldehyde and the like, or a cyclic derivative thereof such as trioxane, into the composition as a binding or complexing agent for the ammonia generated during the gelling reaction. Further, in U.S. Pat. No. 3,306,756, likewise issued to Miller on Feb. 28, 1967, there is described an alkali metal silicate-amide soil stabilization composition of consistently controllable gelation time, which composition additionally incorporates as an accelerator for said gelling reaction, either a carboxylic acid or ester thereof, a ketone, an alcohol, a linear aldehyde other than formaldehyde, including the linear polymers thereof, dioxane, mixtures of these compounds or mixtures of formaldehyde with at least one of said compounds. Still further, U.S. Pat. No. 3,028,340 (Gandon et al.), issued April 3, 1962, describes and claims a composition suitable for soil stabilization comprising an alkali metal silicate in combination with the linear dialdehyde, glyoxal, as hardener for the silicate. Although safer to apply than the aforesaid silicate-formamide formulations since it generates no hazardous ammonia vapors, the silcate-glyoxal composition, however, does not cure to gels of significant load-bearing capacity.